Figure 5. Trajectories of streamflow response over 20- to 30-year periods after forest harvest vary markedly among the three LTER sites where forest harvest was conducted (AND, CWT, HBR). Total streamflow yield was considerably above pre-harvest levels even after 30 years at AND, but had returned to pre-harvest levels within 10 years, and then dipped well below pre-harvest levels, at CWT and HBR. Possible explanations for these differences include the fact that at AND, leaf area and water use of 30-year-old Douglas-fir conifer stands may be much lower than that of the 450-year-old forest that was harvested, whereas early successional deciduous forest species at CWT and HBR may attain pre-harvest leaf area and water use quite rapidly. Differences between CWT and HBR in sizes of soil and snow reservoirs did not appear to affect post-harvest total streamflow trajectories, but at AND the high amounts and strongly seasonal precipitation, combined with deep soil reservoirs may overwhelm the ability of early successional vegetation to utilize water surpluses.
